Experiments are described to produce and analyze T cell clones to M. leprae from normal BALB/c mice using different immunization/infection regimens. T cell clones will be tested for recognition of whole M. leprae and fractionated mycobacterial antigens by lymphoproliferative assay, using whole organisms and nitrocellulose-bound purified antigen. Phenotypic characteristics of T cell clones will be determined using murine T cell subset- specific reagents. The ability of T cell clones to produce IL-2, mediate microbicidal activity on macrophages and to mediate antigen-specific cytolysis of M. laprae-infected target cells will be determined in vitro. Antigen-specific recognition, microbicidal activity and cytolytic function will be tested for H-2 restriction using H-2 matched and non-H-2-matched antigen-presenting or target cells. Also, T cell clones will be tested for their ability to transfer local delayed-type hypersensitivity in the footpads of BALB/c mice. T cell clones with defined antigenic reactivity and phenotypic characteristics will be tested for in vivo activity by transferring cloned T cells to M. leprae-infected BALB/c nude mice. Immunologic function (i.e., activation of macrophages to kill M. leprae) of defined clones will be determine by monitoring the "viability" of M. leprae by measuring intracellular bacillary ATP and the rate of oxidation of 14C-labeled palmitate. Also, histopathologic changes observed in the M. leprae-infected nude mouse footpad will be monitored. Finally, antigens of M. leprae and cross-reactive mycobacteria found to stimulate T cell clones will be characterized and purified using conventional and microanalytical biochemical separation techniques. Results obtained from the experiments may implicate T cells-reactive antigens of M. leprae which are important in the protective immune response to M. leprae infection in mice and by inference in man.